1. Field of the Invention
The invention relates to waste water treatment apparatus, and more particularly to rotating contactors for the biological treatment of waste water.
2. Reference to Prior Art
U.S. Pat. Nos. 4,137,172, 4,549,962, and 4,431,537 are illustrative of the general configuration of rotating contactors for the biological treatment of waste water. Typically, rotating biological contactors (RBCs) include a rotatable contactor mounted in a tank containing waste water. The lower portion of the contactor is submerged in the waste water and the upper portion is exposed to the atmosphere. The contactor is rotated to alternately expose portions of the contactor to the atmosphere and the waste water, thereby providing for the growth of biological organisms on surfaces in the contactor and treatment of the waste water by the organisms.
Rotatable contactors typically include a plurality of discs stacked on a horizontally extending, rotatable shaft. The discs typically are corrugated sheets of plastic, wherein the grooves and ridges defined by the corrugations are straight and thus define straight, unidirectional flow passages. The organisms grow on the disk surfaces defining the passages, and the waste water in the passages contacts the organisms.